# std::weak_ptr<T>::expired

From cppreference.com
< cpp‎ | memory‎ | weak ptr

bool expired() const noexcept; |  | (since C++11)

Equivalent to use_count() == 0. The destructor for the managed object may not yet have been called, but this object's destruction is imminent (or may have already happened).

### Parameters

(none)

### Return value

true if the managed object has already been deleted, false otherwise.

### Notes

If the managed object is shared among threads, it is only meaningful when `expired()` returns true.

### Example

Demonstrates how `expired` is used to check validity of the pointer.

Run this code

    #include <iostream>
    #include <memory>

    std::weak_ptr<int> gw;

    void f()
    {
        if (!gw.expired())
    	std::cout << "gw is valid\n";
        else
            std::cout << "gw is expired\n";
    }

    int main()
    {
        {
            auto sp = std::make_shared<int>(42);
    	gw = sp;

    	f();
        }

        f();
    }

Output:

    gw is valid
    gw is expired

### See also

lock | creates a `shared_ptr` that manages the referenced object (public member function)
use_count | returns the number of `shared_ptr` objects that manage the object (public member function)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/memory/weak_ptr/expired&oldid=174841"